You can cover most of the distances in the city on foot or using local buses. Tickets can be bought either at the kiosks or from the vending machines on the bus (90 cents, exact change). If you buy the ticket on the bus, remember to have coins. All tickets must be validated and are usable for 70 minutes. Various kinds of day passes are also available. Google Maps is blissfully unaware of the bus system in Thessaloniki, so you'll have to install an app like Moovit to figure out how. to get places.